Counterweighted parallel motion arm



ocf.14,1947. @Hmm Em 2,429,132]

COUNTERWEIGHTED PARALLEL MOTION ARM FiledvSept. 22', 1944 5 Sheets-Sheet1 Oct. 14, 1947.

c. H. LITTLE Er Al.

COUNTERWEIGHTED PARALLEL MOTION ARM Filed sept'. 22, 1944 s sheets-sheet2 l 74 75 75 u. iw. mmm. uw m m m a W Z AH, BW M W Oct. 14, 1947. .c.LITTLE Er AL. l 2,429,132

COUNTERWEIGHTED PARALLEL MOTION ARM A Trae/vs ys Patented ct. 14, 1947COUNTERWEIGHTJDBARALLEL MOTION- R Charles Henry Little, ClevelandHeights, and Charles Hubbard Little,-Cleveland, Ohio Applicationseptember 22, 1944, serialNo. 555,217'0 (c1. seais) 12 Claims.

The present invention relates to drafting machines and similar devicescomprising a parallel motion mechanism or arm, one end of which issecured to or is adapted to be secured to a table, drafting board orlike device, affording a Working surface over which the free end of thearm provided with some suitable instrument is adapted to be moved andthe instrument carried thereby maintained parallel in successivepositions.

Where the working surface is inclined, the parallel motion arm, whichusually comprises tWo relatively movable sections, will not remain inany predetermined position without being heldA therein by the operator.In an attempt to overcome this difculty, various counterpoise mechanismsemploying Weights as the counterpoise vforce producing means have beenproposed but none of the counterpoise mechanisms heretofore employedhave been entirely satisfactory for various reasons, such as', that theygive the machine a bulky and ungainly appearance, impose limitationsupon the otherwise normal range of movement of the parallel motion arm,etc,

One of the principal objects of the present invention is the provisionof a novel and improved drafting machine or similar device, including aparallel motion arm and weight-actuated counterpoise mechanism, whichmachine is so constructed and arranged that it Will not have the Aappearance of being bulky and ungainly, and the counterpoise mechanismvvvill not interfere With the otherwise normal range of movement of theparallel motion arm.

Another object of the invention is the provision of a novel and improveddrafting machine or similar device comprising'a Wheel and band typeparallel motion arm and counterpoise mechanism therefor including agravity-actuated Weight located underneath the Working su'rface ordrafting board.

Another object of the invention is the provision of a novel and improveddrafting machine or like device comprising a wheel and band typeparallel motion arm and Weight-operated counterpoise mechanism thereforeffective to balance the parallel motion arm at allV board angles fromzero to ninety degrees.-

Another object of the invention is the provision of a novel and improveddrafting machine or like device comprising a parallel motion arm andcounterpoise mechanism therefor, which counterpoise mechanism isautomatically operable for 4diierent board angles.

Another object of the invention is the provision of a novel and improveddrafting machine or similar device comprising' a Wheel and band typeparallel motion arm andcounterpoise mechanism therefor including aWeight adapted to be located at the side of the'draiting board orWorking surface opposite to said' arm and operatively connected to saidarm by means permitting adjustment of said WeightV angularly withrespect to the arm.

The invention resides in certain constructions and combinations andarrangements of parts and further objects andadvantages will be apparentto those skilled in the art to which it relates from the followingdescription of the preferred embodiment withv reference to theaccompanying drawings forming a part or this speciiication in whichsimilar reference characters designate corre- Spending parts., andinwhich Fria 1,- is a front View of, a drafting machine embodying thepresentinvention attached to a vertical draftingA board;

Fig. 2 is a fragmentary sectiona1 View, With portions in .ematicaVvoli-th devie Shown in Fial, approximately on the line 2-2 of Fig. 1,with both Sections 0f ihepaallel motonrmlvsltimed at right angles @theuppersdggof the drawing board: and Fig. 3 is a fragmentaryA rear View ofthe device shown in Fig. ,1, with the various parts in the PositionsShown .in Fg- 2f Y The drafting machine ShOWrl comprises a jointedtwo-,section parallel vmotion mechanism or arm of the wheel and bandtype having an instrument or protractor head A at one end and the otherend rlxedly secured, as by wood screws l0,

to a verticaldrafting board B. The instrument,

head A is adapted tov be moved about the Workinefsurfeeof the .drawingboard B and the rulersor other instruments `forming a part thereof.; Amaintained parallel by the parallel motion mech-y." anism in` successivepositions to which they are moved- The parallel motion mechanism or armshown, which is the preferred construction, comprises tvvo angularlymovable sections, each comprising a pair of wheels of equaldiameterencircled by a exiblebandand 'lfielrlv in spaced relation withthe band under tension by a strut so constructed as toenclose the band.and wheels. The upper or anchor section of the parallel motion mechanismor arm comprisesthevvheels ll and I2 encircled by an endless band I3andheld in spaced relation by a strut C comprising yokes or yoke mem.-bers |.4'and I 5 kconnected by tubular side members I6 and Il. The upperyoke I4 is pivotally connected to -the vanchor assembly D, of which the3 upper wheel H is a part and through the medium of which the parallelmotion arm is connected to the drawing board B by being ilxedly securedto the front or left-hand end of an elongated bolt or spindle I8rotatably supported in the anchor bracket by anti-friction bearings 20and 2|, 22 and 23 adjacent to A the front, intermediate and rear partsthereof, respectively. The anchor bracket D is made in two parts 24, 25to facilitate assembly of the various bearings and` other parts. Theendless band [3 is separable with the ends thereof detaohably connectedtogether to facilitate assembly and replacement thereof. The tubularside members of the strut C are preferably similar to thosedisclosed'and claimed in our copending application Serial No.

631,334, led November 28, 1945, andare sepa rable intermediate theirends with the adjacent portions thereof connected together by tubelikenut members 2S rotatable in one direction to expand the strut and tensetheband and in the opposite direction to release the'same so that theycan be moved along the side members to expose a portion or portions ofthe band.V

' The protractor section of the parallel motion arm'is of similarconstruction and comprises equal diameter wheels 30 and 3l encircled byan endless band 32 and held in spaced relation by a strut comprisingyoke members 33', 34 connected by tubular'side members 35, 36` includingtubular nut members similar to the tubular nut members previouslyreferred to. rIhe wheels l2 and 35 at the elbow of the arm arepreferably formed integral and are operatively connected to therespective struts by antifriction bearings 31, 38, respectively. Thewheel 3l located at the free end of the parallel motion arm forms apart'of the instrument head A. The construction of the protractor strutis such that it fencloses the wheels and band of the protracto section.y

The instrument or protractor head proper, designated generally as A issimilar in construction tothatdisclosed and claimed*v in our copendingapplication Serial No. 555,268,1iled September 22, 1944, entitledDrafting machine, and is not herein shown and described in detail.Reference is made to the aforesaid application for a complete disclosurethereof. Suffice it to say that the instrument head A comprises a 'rulerassembly F including a normally rotatable member 40 forming one elementof the protractor proper and one or more rulers 4l detachably secured toa ruler or chuck arm 42. In addition, the instrument head comprises anormally stationary protractor element 43 which cooperates with therotatable protractor element 4 0 to indicate the angular position of theruler or rulers, index mechanism including the thumb piece 44, aprotractor clamp 45, and a ruler assembly clamp 46.

The counterpoise mechanism shown comprises a pair of counterpoiseweights or weight members 50,51 located at the side of the `drawingboard B opposite the parallel motion arm and formed integral with pulleywheels 52, 53 rotatably supported by anti-friction bearings 54, 55 upona, bolt 56 fixed in a bracket 51 secured by wood screws 58 to the rearof underside of the drawing board B adjacent to the middle thereof so asnot to unduly affect the balance of the board. The pulley wheels 52, 53are operatively connected to pulley wheels 6061 by flexible members orcables 62, 33 comprising turnbuckles G4 of which there is one in each ofthe two reaches in each cable for tensioning the same.r

The rear or lower pulley or wheel 6B which forms a part of thecounterpoise mechanism for the anchor section of the parallel motion armis keyed or otherwise non-rotatably fixed to the bolt I8 adjacent to itsrear end and the pulley or wheel 6| which forms a part of thecounterpoise mechanism for the protractor or instrument section of theparallel motion arm is rotatably supported on the bolt I8 by ananti-friction bearing 10.

The pulley I is operatively connected to the strut of the instrument orlower section of the arm by an internal gear 1l iixed to the front faceor side of the pulley E I. The gear and pulley are concentric with thebolt 18 and the gear is continuously in mesh with a pinion 12 fixed tothe lower end of a shaft 13 rotatably supported in the bracket D byanti-friction bearings 14, 15. The upper or left-hand end of the shaft13 is provided with a pinion 1S continuously in mesh with an internalgear 11 fixed to the lower or right-hand side of a pulley 18 rotatablysupported on the upper member 25 of the bracket D by an anti-frictionbearing 80. The pulley 18 is operatively connected to an equal diameterpulley 8l formed integral with or attached tothe upper side of the yokemember 33 of the instrument strut by a flexible member or cable 82extending around both pulleys and provided with a turnbuckle 83 fortensioning the same. Any rotation of the instrument section of theparallel motion arm relative to the drafting board or any force tendingto rotate the same is transmitted by the cable 82, pulley 18, etc., tothe ,pulley 6I and from thepulley 5l to the weight 5I by the flexiblemember 63.

-The effective weight of the counterpoise weight members 5G, 5l may beadjusted, if desired, in any suitable manner. As shown, the weightmembers 5D, 5| include supplemental members 84, 85, slidable upon rods8S, 81 fixed to the members 55, 5 l, respectively. The supplementalmembers 84, 85 are adapted to be secured to the rods 86, 81 in anyadjusted position by set screws or the like. If desired, a supplementalbracket or base 88 may be connected to the lower or rear side of theAanchor bracket D and to the lower or rear end of the bolt` 56 for thepurpose of relieving the drafting board B of some, if not al1, of thestrain produced therein by the tension of the cables 62, 63. l

The flexible members'or cables 62, 63, as shown, encircle the pulleywheels 52, 68 and 53, 6|, respectively, and are preferably connected tothe wheels by screws 89. This construction reduces the amount of tensionwhich would otherwise be required to prevent the wheels from slippingwith respect to the cables.` If more rotation is desired than thatpermitted by the con-struction shown, it will be obvious that the cablesmay be looped about the pulleys a greater number of times or theconnection 89 therebetween and the pulleys omitted.

The two turnbuckles employed in each of the cables 62, 63 are for thepurpose of tensioning the cables and permitting the weights to beangularly adjusted slightly with respect to the sections of the parallelmotion arm with which they are associated. It will be apparent that ifonly one turnbucklewasemployed, the angular relationship between theweights and the arm would be disturbedeverytime that the cables weretightened. Alternatively, other means may be employed for adjusting theangularity of the weights with respect to the arm, for example,provision lmay be made for adjusting the weights Vrelative 1to thepulleys 52, 53, the pulley 6U relative to the spindle le, er the. pullerel relative te the pill: lex 18..

it is believed that the. egeiratieii ef the .eleviee will. be. apparent.frein the feregeirie. deserpten. tnerecrlrieilv, when trie parallel.metten. arm le petitioned at rient angles. tc the ripper ed'ee 0f tlie.drawing. beard, the center. et gravity f the ccnnterpclee weights isdirectly between the belts le, te., ariel. the weights. cle riet tend teretate the Parallel greifen eirrri de the. errri. 0r either Setticnthereef` ie moved clit 0f the aforesaid reel-r tion, the center ofgravity of the weight connected te. the Section. le reared te erle Sideer the ether ci trie lirie eeniieetirre the/beltelit ariel.decerielirie. uren Wirth trie. eeetienie tiered., with. the result. thatthe, weielit. 0rvieleiita balance eeirriterpeise the paralleli mettenarm.- tfie also. tc. be noted. that the. eecnterpeieirie effect ef theweights varies as the. beard. ariele le elcarieea trie. result ci, whichle, that theceunterreiee mechaaien le cperalele ier all beard' allelesWithout attention en the. part ei'tliev operator er., inV etherl Werde,is automatically alterable vier different. board angles.'

Eiern the foregoing description. ci the preferred einbedimerits 0ftheinveriticn, it Will be apparent that theA Objects heretoforeenumerated and others have been accomplished. and that a nevel andimprovedJ drafting machine cr. like device hasbeen provided comprisingccnnternlse mechanism. of. imprinted design andccnstruction, whichcounterpoisemechanism does not interfere, with .the otherwise fullmovement of the. parallel mo.-

tiQn arm, does not.` givetheA device a bulky and ungainlyalpearance, isout of the way of the operator, and. is eiective throughout the rangefimove'ment of the parallel. motion'v arm and for all,` dierentfboard'angles.

'While the 'preferred embodiments of the invention have 'been' describedwith considerable detail, the inventionis' not 'limited to the par-` vorarm of the wheel and banditype adapted to have connected one endthereofr to a drawing board or theVV like, 'counterpoise means for asec-v tioaof 'the parallel motion drin, Comprising a weightV adapted tobe pivotallysupported at the side of the' drawing board opposite theparallel motion arm for` rotation at, a constant predetermined., radiusabout anV axis.: at right angles to the2 working surface ofthe' drawingboard, and fo".v operatively connecting .said Weight toasection"of's'aidarm'.v

2. In a drafting` machine or like device including a multi-section,wheel and band type, parallel motion mechanism or arm adapted to haveone end thereof connected to a drawing board or the like, a weight forcounterpoising a section of said arm, means adapted for pivotallysupporting said weight at the side of the drawing board opposite saidarm for rotation at a constant radius about a fixed axis, meansincluding two relatively rotatable members for operatively connectingsaid weight to the section of said parallel motion arm to be balancedthereby, and

eaiei @enters aiierilarlr relative t`eac'h other. n 3. In a drafting'machine or like device in; cluoling a multi-section, parallel motionmecha'- nism or 'arm etlptedfto have. one. end thereof -connectedtohamdrUig boardor. the like,` counterpoise meansI 'for each se'tenori of saidparallel motion arnsoconstuc'ted as to permit` rotation of 'saidarnthicpgh substantially ecce and come riisiiie 'ccaiite're e? iree;melueirieraeeri-ariieli1 ity' Of Weights. Piretellv elle.: pcntedY atthefside of said drawing board opposite the'plaraiiei in'ticii afm roilrotation at acon; Staet'rallii 'erteilt' a. iiirecl'axie, and means ferconnecting aid weight to'fsaid arm.` n

Il'.v In"a"d`rafting machine or likeI device in,- cluding amulti-section'parallel motion mechanism or arm adapted tohave. one endthereof connect'edftd a "dra'wmg board or they. like, meansfoncounter'poising ythe sectic'uiv of said parallel motion arrn 'atth"free, endl thereof when it pro: jectstoV veither s" e, ofr thelongitudinal center line"of the sectionfto which it is connected, saidmeans comprising aY weight` pivotally supported at the sic'iebf saiddrawing. board opposite the parallel motion yarm for. rotationV at'accnstant radius about an axis atright angles tothe. work.

Ineens. ier ediuetlrle ingy s'i'irfaceof Ysaid drawing 'board` and meansfor connecting saidweight vto the, arm.

"5, In v`a drafting" machine. or like. device. including a parallellfriction,v meclfianismI on arm adapted to beconnected toa drawing.'boardY or tlielikefor movement. over at leaat a, portionv of one sidethereof, av weight; for. co'unterbalancing said arm, said'weglit beingadapted'tcbe pivotally connected'tothe sideof said'drawing boardcppcsite'the" parallel motion' arm and adjacent to .the .center thereof-for rotation at a constant -pr'edeterminedradius about. axisv at rightangles to the working surfaceX of the drawing board, andineansfor'.roperatively. connectingI said weight tolsaidlcaraiia mctigamechanism;

6. In a'draftingnachine or likedevice a paral? lel motion mechanism orv4a'rn'i adapted to .be con,- nected Vto adrawing board or the like formove,e nient over at leasta portion 'offone side thereof, a weightpivotally supported at thel side. of said drawing boardA opposite the.`parallel motion arm for, counterbalancing said arm, and `means in;ellittica iilterriaileeare. leeat'eii.Y .at credette Sides ef, thedrawing. beard arid; ceririeeltetl by. eleriait providedk with pinionsmeshing with said gears fer iteratively eenrieetirie. 'Salti Weielittetti- 1 arm.

7, In a drafting machine-orlike device a paralleal motion mechanian orarm adapted to be connected to agdrawing board of the. like for move;-ment over at least, a portion ofl'cneA side thereof, a, Weight adaptedkto bev pivotallyA connected v`to the side of saidvdrawing board oppositethe parat lel motion arm for counterbalancingl said arm, and AmeansincludingY apair ofy Wheels encircled by a flexible member foroperatively connecting said weight to said parallel motion arm.

8. In a drafting machine or like device a parallel motion mechanism orarm adapted to be connected to a drawing board or the like for movementoverat least a portion of one side thereof, a weight adapted to bepivotally connected to the side of said drawing board opposite theparallel motion mechanism for counterbalancing said arm, a spindleextending to opposite sides of said drawing board, means for operativelyconnecting one end of said spindle with said parallel motion arm, andmeans including a pair of wheels encircled by a flexible member foroperatively connecting said weight to the opposite end of said spindle.

9. In a drafting machine or like device including a multi-section,parallel motion mechanism or arm having an instrument adjacent to oneend thereof and means adapted to connect the other end of said arm to adrawing board or the like, a weight adapted to be pivotally connected tothe side of said drawing board opposite the parallel motion mechanismfor counterbalancing the section of said arm at the free end thereof, aspindle extending to opposite sides of said drawing board, pinions onopposite ends of said spindle, an internal gear in mesh with said`pinion adjacent to said arm, means comprising a pair of wheels encircledby a flexible member for operatively connecting said internal gear tosaid section, an internal gear in mesh with the other of said pinions,and means including a pair of wheels encircled by a flexible member foroperatively connecting said weight to said last-named internal gear.

10. In a drafting machine or like device adapted to be used on aninclined drawing board or the like, an anchor member adapted to beconnected to a drawing board or the like, a wheel fixed with respect tosaid anchor member and adapted to be located at one side of the drawingboard to which the anchor member is attached, a strut rotatablysupported concentric with said wheel, a second wheel spaced from saidrst wheel, means for pivotally connecting said second wheel to saidstrut, a flexible band encircling said wheels, a third wheel concentricwith said second wheel and fixed with respect thereto, a second strut,means for `pivotally connecting said second strut to said third wheelfor rotation about an axis concentric therewith, a member locatedadjacent to said rst wheel, means for supporting said member forrotation about an axis concentric with the axis of said first strut,means for operatively connecting said member with said second strut, aweight for counterpoising said second strut and adapted to be located atthe side of the drawing board opposite said wheels, and means foroperatively connecting said weight to said member.

11. In a drafting machine or like device adapted to be used on aninclined drawing board or the like, an anchor member adapted to beconnected to a drawing board or the like, a wheel xed with respect tosaid anchor member and adapted to be located at one side of the drawingf second Wheel and fixed with respect thereto, a

second strut, means for pivotally connecting said second strut to saidthird wheel for rotation about 8 an axis concentric therewith, a fourthwheel located adjacent to said rst wheel, means for supporting saidfourth wheel for rotation about an axis concentric with the axis of saidfirst strut, a iifth wheel concentric with said second and third wheelsand xed to said second strut, a iiexible band encircling said fourth andfifth wheels, a weight for counterpoising said second strut and adaptedto be located at the side of the drawing board opposite said wheels, andmeans for operatively connecting said weight to said fourth wheel.

12. In a drafting machine or like device adapted to be used on aninclined drawing board or the like, an anchor member adapted to beconnected to a drawing board or the like, a wheel xed with respect tosaid anchor member and adapted to be located at one side of the drawingboard to which the anchor member is attached, a spindle rotatablysupported in said anchor member concentric with said wheel and adaptedto extend to opposite sides of the drawing board, a strut fixed withrespect to said spindle, a second wheel spaced from said rst wheel,means for pivotally connecting said second wheel to said strut, aflexible band encircling said wheels, a weight adapted to be located atthe side of said drawing board opposite said wheels, means foroperatively connecting said weight to said spindle, a third wheelconcentric with said second wheel and xed with respect thereto, a secondstrut, means for pivotally connecting said second strut to said thirdwheel for rotation about an axis concentric therewith, a fourth wheelspaced from said third wheel, means for pivotally connecting said fourthwheel to said second strut, a flexible band encircling said third andfourth wheels, a fifth wheel located adjacent to said rst wheel, meansfor supporting said fth wheel for rotation about an axis concentric withthe axis of said spindle, a sixth wheel concentric with said second andthird wheels and fixed to said second strut, a flexible band encirclingsaid fth and sixth wheels, a second weight located adjacent to said rststrut, and means for operatively connecting said second weight to saidfifth wheel.

CHARLES HENRY LITTLE. CHARLES HUBBARD LITTLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

